In recent years, with high functionalization of electronic devices such as smartphones, tablets, and notebook computers, densities of heat generation from heat-generating components have drastically increased. Therefore, heat-insulation technologies have been indispensable, for such electronic devices.
In particular, small-sized mobile devices have many occasions to come into direct contact with human bodies, and increases in temperatures of external surfaces of their casing have been serious problems. As one example of problems caused by such increases in temperatures of external surface of casings of mobile devices, low-temperature burn injuries are a type of burn injury caused by long-term exposure of the human body to a temperature higher than the body temperature. There has been a report that, when the temperature is 44° C., burn injuries will occur in 6 hours, and that the time required to result in the burn injuries will be shortened to half of it by an increase of 1° C. Compared with usual burn injuries, in most cases of low temperature burn injuries, injured persons take longer to notice the progression of the symptoms. When the injured persons eventually notice the injuries, they have already received serious skin damages in most cases.
Moreover, liquid crystal or organic EL displays are used for display elements of mobile devices. However, these display elements are weak to heat, and, if heat from heat-generating components transmits to the display elements, this becomes a factor that causes uneven brightness or reduced durable life of the displays. Therefore, in order to satisfy both of high performance and reduced size/thickness of the mobile devices, it is required that the heat transmission to the display elements is effectively reduced.
Furthermore, recently, there are many cases where low temperature burns injuries occur when small-sized notebook computers are used on the knees for a long time. In a state where downsizing of devices, and development of their mobile forms will be increasingly progressed in the days ahead, it is a most important issue to keep the temperature of the surface of the devices as low as possible even by 1° C.
Additionally, miniaturization, thinning, and high functionalization of appliances such as audio visual equipment (e.g. televisions, recorders, and audio instruments), white goods (e.g. air conditioners and washing machines), and electric tools (e.g. electric screwdrivers) have growingly progressed. These appliances also have occasions to come into contact with human bodies, and therefore, there is an increasing need for suppression of heat transmission to external surfaces of the casings.
Furthermore, with regard to residential building materials, there is an increasing need for thinning of walls, and narrowing of piping routes in association with expansion of indoor spaces. Even when walls are thin, heat-insulation performance of rooms must be maintained. Therefore, it is required to block the outside cool or warm air. Heat insulation is required also in order to prevent dew formation on/in pipes. In addition, in cases where hot water flows through pipes, heat insulation is required in the pipes.
As one example of a method for blocking the heat to solve the above problems, use of heat-insulation members in the electronic devices or home electric appliances can be considered in order to prevent the heat from heat-generating components inside casings of the devices or appliances from transferring to the casings. Also, use of heat-insulation members is considered to block the heat in the field of residential building materials. Furthermore, in order to fulfill these demands, there has been an increasing demand for realization of thin and flexible heat-insulation materials.
As one example of a heat-insulation member that satisfies the above demand, a sheet-shaped heat-insulation material that is obtained by causing a substrate such as unwoven fabrics to contain a highly-heat-insulative aerogel can be mentioned. However, when such a heat-insulation sheet based on an aerogel is used as a heat-insulation material, the sheet cannot be adhered to a desired location since the aerogel is adhered onto surfaces of the sheet. To solve this problem, there is a structure shown by a cross-section diagram of FIG. 8 (JP-A-2009-299893, JP-T-2001-509097, etc.). In the structure, a surface of an aerogel layer 101 is covered with a covering layer 102.